In various applications, it may be beneficial to etch a metal substrate, such as copper. In some embodiments, sputtering or plasma etching may be used to remove a layer of metal from a particular region of a substrate. For example, it may be advantageous to create a trench, hole or channel in a metal substrate. To do so, a mask layer may be applied to portions of the metal substrate, leaving exposed the region to be removed. Next, a plasma etching or sputtering operation may be performed which removes metal from the exposed region. While this process does remove the metal, there may be several disadvantages. First, the etch process may not create a trench, hole or channel that has vertical sidewalls. In other words, the sidewalls may taper inward in the trench. Secondly, an etch process may produce species that are unstable or have limited volatility, which may later deposit on other surfaces, such as the mask layer. Finally, the rate of metal etching may be slow, impacting manufacturing yield and cost.
Therefore, it would be beneficial if there were an improved method for etching metal substrates that created more vertical sidewalls without producing unwanted metal particles. In addition, it would be advantageous if there were an apparatus that implemented this method.